Waveform chart x-axis time value changes

[GoncaloPT]

Hi everyone,

I'm a recent labview user, and i am trying to set a waveform chart to represent the values received. Everything is running good, except the fact that the x-axis (that i set to min.0 and max.300 seconds), when i run the VI, changes its value to something else...the values back to estipulated only when i clear chart, and if i run it again happens the same thing, over and over... Another question is the data. when i set the run time to 120 seconds at the end the data aquired erases a portion of samples at the beginning....

If someone could help me i'd appreciate it

P.S. Sorry for my bad english, i'm portuguese...

[RavensFan]

A chart has a history length, which by default is 1024.  That means it holds up to 1024 samples, as samples beyond that get written to the chart, the old ones at the beginning disappear.

You also have some issues with your DAQ assistant.  You are reading only 2 samples at a 100 Hz rate.  But your while loop is throttled to 100 msec.  So in one loop iteration which takes 1/10th of a second, you've accumulated 10 samples, but are only reading 2 of those.  The remaining 8 stay in the buffer until the next loop iteration.  Now you have 18 in the buffer but only read 2.

I don't know why you have your blue wire going to a boolean indicator as well as numeric indicators.  Or why you use the Select signal VI's to break up the original blue data wire, only to remerge the signals all together for the waveform chart.

[GoncaloPT]

Thanks a lot Raven. Really appreciated. Now i'll make the changes you suggested me and than i'll show you the "new" VI.

Many thanks

[GoncaloPT]

Hi again...

Can anyone tell me how can I separate the signals if not by "select signals" function? I have 4 channels and i need the respective 4 charts in the same graph...

Thanks for your help

[shjukheter]

You mean this..

[GoncaloPT]

My Daq receives 4 channels data, what i meant was to aquire those 4 data in my waveform chart...does this solve my problem? I've tried it already but didn't worked...maybe i forgot something... What i really want is to split my signals on the waveform chart...

[shjukheter]

I saw your personal mail and therefore I am replying here.

I don't understand first what you are trying to do. BTW, have you made any search on forum.

See this http://forums.ni.com/t5/LabVIEW/how-do-i-display-multiple-plots-on-one-chart/m-p/803352/highlight/tr...

I don't get any data in your VI and I don't have any DAQ unit to check. Whenever, if you are going to post any VI on this forum, first save it as Go to-->EDIT--> Mark current values as default.

[Dennis_Knutson]

To display all channels on your chart, just wire the chart directly to the output of the DAQ Assistant.

[GoncaloPT]

Now it's working great!!!

Thanks a lot you guys.